1. Make a double thickness foil tray about 20cm square. Par-boil the new potatoes in lightly salted boiling water for 3-4 mins. Drain and rinse under cold water.
2. Toss potatoes with the peppers, aubergine, courgette, mushrooms, tomatoes, red onion, oil and vinegar. Position the foil tray on the barbecue grill, then add the veg. Season, then cook, turning frequently, for 10-15 mins until tender and browned.
3. Spoon into a serving bowl and toss with the dressing ingredients.